// reference count

const user1 = {age:11}
const user2 = {age:22}
const user3 = {age:33}

const nameList = [user1.age,user2.age,user3.age]//user1到3还被这个数组引用着，不会被回收

function fn(){
    const num1 = 1
    const num2 = 2
}

fn()//当函数调用完毕后，num1和num2无法被外部使用，引用计数为0会被回收
